1. Field of the Invention
This invention relates to the field of gearshift mechanisms for manual transmissions and, more particularly, pertains to the portion of such a mechanism located in the vicinity of the selector finger and check plate.
2. Description of the Prior Art
German patent No. 30 03 076 describes a shift mechanism that includes a selector finger secured to the selector shaft by a hub, which is surrounded by the hub of a check plate guided on the selector shaft. This mechanism does not include a spring-loaded catch device or detent for holding the selector shaft in several axial positions with respect to the transmission casing or any other reference position. Conventional gearshift mechanisms that include detents locate the detent in a bore on the transmission casing.
The arrangement of such a gearshift catch device located separate from the gearshift and locking mechanism has the disadvantage that the accumulation of dimensional tolerances, which arise during manufacturing and assembly, cause substantial discrepencies between the gearshift positions determined by the spring-loaded catch mechanism and the actual gearshift positions of the gearshift members.
The gearshift mechanism described in German Patent No. 32 45 529 includes a selector shaft displaceable axially for preselecting gearshift channels or planes and rotatable angularly for engaging the gear speeds. In this shift mechanism, to avoid tolerance problems, the spring-loaded catch device is located between a pivotal selector finger and the check plate, whose position is fixed to prevent pivoting. The spring-loaded catch includes a helical compression spring, which surrounds the selector shaft and acts on a locking ring. The ring receives a ball mounted rotatably and cooperating with corresponding catch recesses in the check plate.
The gearshift apparatus of German Published Specification No. 16 80 046 includes a selector shaft, axial displaceable for preselecting gearshift channels and radially pivotable for engaging the selected gear speed. To simplify assembly in this mechanism, a spring-loaded catch device is located between a rotatably pivotal selector finger and a radially fixed check plate. The selector finger is provided with a cylindrical extension for receiving a spring-loaded ball catch, Which cooperates with corresponding recesses in a member connected to the check plate. The catch recesses extend over the axial path of the selector shaft, which is required for the preselection of the gearshift channel. The structural complexity is relatively substantial and the number of components of this mechanism is large.